Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$235.85	8.142%	$255.0529	$255.05	$255.05	$255.10
Purchase #2	$39.67	13.117%	$44.8735	$44.87	$44.85	$44.90
Purchase #3	$177.98	3.453%	$184.1256	$184.13	$184.15	$184.10
Purchase #4	$246.64	3.627%	$255.5856	$255.59	$255.60	$255.60
Purchase #5	$239.51	7.702%	$257.9571	$257.96	$257.95	$258.00
Purchase #6	$208.80	11.624%	$233.0709	$233.07	$233.05	$233.10
Purchase #7	$160.68	6.593%	$171.2736	$171.27	$171.25	$171.30
7 purchase totals =	$1,309.13		$1,401.9392	$1,401.94	$1,401.90	$1,402.10